The present invention relates to the field of radiotherapy devices, and more particularly to the field of implantable, permanent or retrievable radiotherapy devices. More particularly still, the present invention relates to the field of shielded radioactive wires adapted for implantation at the site of a lesion or other selected body tissue for treatment of cancer or other pathological condition.
At present, external beam radiotherapy is widely utilized in the treatment of cancer and more recently, in the treatment of vascular malformations particularly those affecting the Central Nervous System. Radiotherapy is used as an adjunct to surgical excision and chemotherapy, or as the sole form of treatment.
External beam radiotherapy can be either nonfocused or stereotactic using a gamma knife apparatus or a linear accelerator. Both of these radiotherapy modalities are limited by the undesirable side effect of radiation necrosis they produce in the normal tissue surrounding the lesion to be irradiated.
Interstitial brachytherapy is a form of therapy which delivers local radiation to a lesion using permanent implants (seeds) which are surgically inserted in or very close to the area of interest. Theoretically, brachytherapy allows the delivery of a high dose of radiation to the abnormal or cancerous tissue with minimal or limited damage to the adjacent normal structures. Interstitial brachytherapy is often utilized to supplement surgical excision of a tumor or in combination with external beam radiotherapy. The permanent implants used in interstitial brachytherapy are inserted in the tumor bed during direct surgical exposure or utilizing a stereotactic localization device.
It would be desirable to provide a brachytherapy device that can be inserted percutaneously in cancerous lesions or vascular malformations through a microcatheter introduced in the body via the arterial tree, the venous system, or any other physiologic collecting or drainage ductal system. This would provide a relatively simple, cost effective, and medically effective treatment which would also be relatively easy to implant in the patient's body. Using a procedure of this type would in most cases be less traumatic to the tissues involved, and would thus be less risky than traditional methods of interstitial brachytherapy. In addition, it would be desirable to provide such a brachytherapy device that can be retrieved and replaced if necessary or desired, or left permanently in place.
Presently, there are several types of embolic devices available which can be introduced in the arterial or the venous system through a microcatheter. One such device is in the form of a thin metallic coil or a thin composite metallic wire that can be preloaded in a polyethylene sheath and introduced percutaneously into the area of interest through the microcatheter. This known device can be delivered using a controlled delivery mechanism or simply injected through the catheter.
The embolic devices referred to in the previous paragraph are currently used for their thrombogenic effect to occlude blood vessels. It would be advantageous to use such known systems not only for such purposes, but also for the dual purpose of an implantable radiation device. This way, the simple, effective delivery systems now known for thrombogenic treatments can also serve as radiotherapy delivery systems.